RU2414439C2 - Method of producing cement - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to cement compositions and can be used to produce cement used in construction. The method of producing cement involves preparation of a crude mixture by grinding components - basic carbonate filtration residue from sugar production, obtained from filtration of saturation juice I on chamber filter presses, and additional components which contain clay and iron-containing material, mixing said components, high temperature burning of the crude mixture, cooling, obtaining a commercial grade product by grinding the obtained cooled mass to the required particle size. Before grinding, the said residue undergoes thermal treatment at 300-1000°C. The dried residue and additional components undergo fine grinding separately before mixing and are then burnt in a rotary furnace. The carbonate material additionally used is chalk or limestone in a mixture with the said residue.

EFFECT: high activity of clinker, low fuel consumption for burning said clinker, reduced dust formation and load on electrical filters.

2 cl, 6 tbl, 1 ex

Description

The invention relates to compositions of cements and can be used to obtain cements used in construction.

A known method of producing cement, including calculating the composition of the raw mix, preparing the raw mix from the carbonate component from the group: filter press mud, limestone, chalk, clay and iron-containing components, firing the raw mix in a rotary kiln at 1450 ° C and obtaining the finished Portland cement from clinker (RU 2122984 C1, 12/10/1998).

The disadvantages of this method are the lack of homogeneity and low reactivity of the raw material mixture.

The technical result of the invention is fine grinding and high homogeneity of the raw material mixture, strong and uniform burning of clinker, its sharp cooling, completeness of CaO binding, which increases clinker activity and reduces fuel consumption for its burning, as well as reducing dust formation and load on electrostatic precipitators.

This result is achieved by the fact that in the method of producing cements, including the preparation of the raw material mixture by grinding the components - the main carbonate - filter cake of sugar production obtained by filtering juice I saturation on chamber filter presses, and additional, containing clay and iron-containing raw materials, and mixing them , high-temperature firing of the raw material charge, cooling, obtaining a marketable product by grinding the resulting cooled mass to the required size, characterized in that the decree ny precipitate before crushing is heat treated at 300-1000 ° C, fine grinding said dried sludge and said additional components are carried out separately before mixing, and calcining given - in the rotary kiln.

Also, the main carbonate feedstock is additionally used natural carbonate feedstock - chalk or limestone mixed with the specified sediment.

Sugar production filter cake (defecate) containing 60-80% CaCO ₃ and 20-40% organic and mineral impurities, as well as up to 0.15% potassium, 0.4% nitrogen, 0.7%, is used as the main carbonate feedstock. phosphorus oxide (as a percentage of the solids solids).

The optimal ratio of SiO ₂ to Al ₂ About ₃ in the filter cake for cement with high strength properties is a value of 3.5-3.8, not higher than 4; the content of tricalcium aluminate 3CaO · Al ₂ O ₃ (C ₃ A), providing strength in the early stages of hardening, will be optimal. If the ratio of SiO ₂ to Al ₂ O ₃ is greater than 4, then it will be necessary to use an aluminum-containing additive to prepare the optimal composition of the raw material mixture, the larger this ratio, the greater the amount of aluminum-containing additive (for example, bauxite with a content of 51.2% can be used Al ₂ O ₃ ). If the ratio of SiO ₂ to Al ₂ O ₃ is less than 3, then for the preparation of the optimal composition of the raw material mixture, additional use of sand or clay with a high content of silica will be required.

The filter cake obtained by filtering the juice of saturation I on chamber filter presses is sent to the dryer, where it is heat treated at a temperature of 300-1000 ° C, during which organic impurities are removed. The dried filter cake is sent to the component bin.

The filter cake can be used both independently and in a mixture with chalk or limestone.

The dried filter cake and additional components for clinker preparation: clay raw materials, iron-containing raw materials, sandstone, are subjected to separate fine grinding in crushers.

Ground components are sent to component bins.

Using a dosing system, the filter cake and all the crushed components are mixed in a certain proportion and sent to the silo of the finished mixture to adjust its composition to the specified parameters and to homogenize by mixing with compressed air.

From the silo, the finished mixture is sent for firing in a rotary kiln, in which the mixture is dehydrated and partially decarbonized at a temperature of 1250-1450 ° C. After firing, the mixture is fed into the clinker cooling chamber. The chilled clinker is sent via a rake conveyor to the finished clinker warehouse. With further grinding, cements can be produced up to the grade PTs500 according to GOST 10178-85.

Example.

In studying the suitability of the filter cake for cement, the following components were used: carbonate - a mixture of filter cake of the Dmitrotaranovsky sugar plant obtained in sugar beet production by filtering juice I saturation on chamber filter presses and defecate with a moisture content of 21.4% and a humidity of 28.6% in 1: 1 ratio, Belgorod chalk with a moisture content of 15.6%, clay - Belgorod clay with a moisture content of 10.4%, bauxites of the Arkhangelsk region, iron - slag of the Oskol Electrometallurgical Combine nata (OEM). The chemical composition of raw materials is presented in table 1.

Table 1 The chemical composition of raw materials, wt.% Material p.p.p. Al ₂ O ₃ Cao SiO ₂ Fe ₂ O ₃ MgO SO ₃ R ₂ O chlorine other Filtration sediment of the Dmitrotaranovsky sugar factory 46.46 0.48 48,20 1.81 0.27 1.24 0.63 0.02 0.01 0.88 Chalk Belgorod 43.00 0.30 54.49 1.21 0 0 0 0.20 0.01 0.69 Clay Belgorod 7.49 13.60 2.20 67.40 5.40 1.73 0.02 1.78 0.04 0.34 OEMK slag 10.43 3.39 38,0 18.22 18.00 8.91 0.10 0.01 0.04 2.88 Bauxites of the Arkhangelsk 18.30 51,20 0.36 16.74 10.90 0.40 0.66 0.40 1,04 0

The ratio between the content of the main oxides CaO, SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ in the raw materials should provide the optimal chemical composition of the raw mixture to obtain high-quality clinker (Table 2).

table 2 The approximate content of basic oxides in the feed mixture, wt.% SiO ₂ Al ₂ O ₃ Fe ₂ About ₃ Cao 14.0 ± 0.5 3.7 ± 0.1 42.0 ± 0.5 14.0 ± 0.5

To calculate the composition of the raw mixes, the “Charge” program developed according to generally accepted methods was used. The calculations of the component composition of raw mixes were performed (Table 3)

Table 3 The composition of the raw mixes, wt.% Mixture Defecate of the Dmitrotaranovsky sugar factory Chalk Belgorod
sky Clay Belgorod OEMK slag Bauxite Kn The set (received) module silicate n alumina p No. 1 76.27 - 14.91 7.32 1.49 0.92 2.2 1.35 Number 2 52.67 22.58 15,52 7.67 1,56 0.92 2.2 1.35 Number 3 37.30 37.30 15.92 7.87 1,61 0.92 2.2 1.35

Before mixing with the other components, the defecate was subjected to heat treatment at 600 ° C to remove organic impurities and dried to a moisture content of 2%, after which it was triturated until it completely passed through a No. 008 sieve. The remaining components were co-milled until passing through a No. 008 sieve and mixed with milled defecate.

Thus, the raw material mixture for clinker was obtained by separate grinding of the filter cake and other components, their subsequent thorough mixing, homogenization, averaging, and adjustment to the desired composition in the dry state.

The reactivity of raw mixes was determined by the intensity of the process of mineral formation, characterized by the amount of Ca free (CaO _sv ) at temperatures of 1250, 1350 and 1450 ° C without exposure. 2 g tablets were prepared from raw mixtures, which were placed in a cold oven, heated to a certain temperature, removed from the oven and placed in boxes. The CaO content was determined Speck alcohol-glitseratnym _{communication} method.

Table 4 The content of CaO _sv in the cakes of raw mixes when heated, wt.% Temperature ° C No. 1 Number 3 1250 15.89 18.65 1350 8.21 10.67 1450 without exposure 1.47 4.33

Thus, it was found that the assimilation of CaO _sv and the processes of mineral formation at a higher content of filter cake in the feed mixture proceed more intensively.

Cement clinker was fired in a rotary mixture at a temperature of 1450 ° C for 40 minutes. Mixtures №8, 9, 10 and the raw meal to Portland cement Starooskolsky not containing filter cake (for comparison) was calcined at the same time, the content of CaO in all clinkers _binding was less than 1%.

The chemical and calculated mineralogical compositions of clinkers are presented in table 5.

Table 5 Chemical and mineralogical compositions of clinker Clinker SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ Cao MgO SO ₃ R ₂ O C ₃ S C ₂ S C ₃ A C ₄ AF No. 1 21.11 5.51 4.08 64.90 3.05 0.82 0.47 60.0 19.0 8.2 12.8 Number 2 21.25 5.55 4.11 65.33 2.60 0.56 0.55 60.3 18.5 8.1 13.1 Number 3 21.34 5.57 4.13 65.61 2,30 0.41 0.59 61,4 17.6 8.0 13.0 Starooskolsky 22.00 5.69 4.03 67.10 0.82 0.06 0.42 61.9 17.6 8.2 12.3

To determine the strength of cement, clinker was ground with 5% gypsum to a specific surface of 290-310 m ² / kg. Then, according to the generally accepted technique, small samples of 1.41 × 1.41 × 1.41 cm in size were formed from a test of normal density. The samples hardened for 24 hours in humid conditions in a bath with a hydraulic shutter, then in water with a temperature of 18-22 ° C. For comparison, the industrial portland cement PC 500-D0 with a specific surface area of 290 m ² / kg was also formed. Strength was determined in scarlet samples according to GOST 310.4-85 (table 6).

Table 6 The strength of laboratory cements, reduced to the results according to GOST, MPa Aged cement No. 1 Number 2 Number 3 PC 500-D0 3 days 26.5 27.6 28.1 29.2 28 days 40.5 48,2 51.3 52.6

Thus, the strength of the cement according to the invention using dried filter cake may correspond to grade 500. The tested cements are quick-setting. This reduces fuel consumption for clinker firing, as well as dust formation in the furnace and the load on electrostatic precipitators.

This method allows you to utilize the filter cake of sugar production, which will be an important technological solution in resource conservation and environmental protection.

Claims (2)

1. A method of producing cement, including the preparation of a raw material charge by grinding the components — the main carbonate — filter cake of sugar production obtained by filtering the juice of I saturation on chamber filter presses, and additional ones containing clay and iron-containing raw materials, and mixing them, high-temperature firing of the raw material mixture , cooling, obtaining a marketable product by grinding the resulting cooled mass to the required particle size, characterized in that said precipitate is subjected to grinding before grinding ayut heat treatment at 300-1000 ° C, fine grinding said dried sludge and said additional components are carried out separately before mixing, and calcining given - in the rotary kiln. 2. The method according to claim 1, characterized in that the main carbonate feedstock is additionally used natural carbonate feedstock - chalk or limestone in a mixture with the specified sediment.